As shown in FIG. 6, in a fluidized-bed incinerator 5, fluidized sand of a fluidized bed 11 constituted by the fluidized sand circularly supplied to the lower portion of the incinerator is preheated to a temperature of about 600.degree. C., and fluidizing air 16 allows the sand to flow. In this state, combustion materials supplied from a charge chute 2 are combusted for a short time. An unburnt gas on the fluidized bed 11 is combusted by secondary air 15 supplied to a free board portion 13, and a combustion exhaust gas 14 is exhausted from a top portion of the incinerator 5.
Uncombustibles contained in the combustion materials are exhausted from the bottom portion of the incinerator 5 together with the fluidized sand. The fluidized sand is separated from the uncombustibles and recycled in the incinerator.
Even in an incinerator for performing combustion processing of waste, a combustion system of the incinerator must be appropriately controlled. Especially, since a charge rate of waste charged in the incinerator is a factor to be managed as a load of a combustion control operation, a means for appropriately measuring the supply rate of waste is required.
In a conventional means for measuring an amount of waste, as is disclosed in Published Unexamined Japanese patent application No. 53-148165, an oxygen concentration in an exhaust gas is detected, and a charge rate of waste is indirectly estimated. Thus, a supply rate of waste is controlled on the basis of charge rate data obtained by the estimation.
As another means, incineration waste is directly measured using a meter, and a combustion control operation is performed on the basis of the measurement data.